1. Field of the Invention
The present invention relates to a mobile telephone, and more particularly to leading tone structure of a mobile telephone.
2. Description of the Related Art
The total number of parties to contracts of a mobile telephone and a personal handyphone system (PHS) exceeds 82 millions of people in Japan (at a time point of the end of June, 2003). Thus, the mobile telephone and the PHS have become items which are generally possessed.
Each of those electronic apparatuses has a telephonic communication function as a main function. Thus, in those electronic apparatuses, the quality of a loudspeaker for reproducing incoming audio data becomes important. As a matter of course, it is required for the loudspeaker to allow reproduction of incoming audio data at tone quality of high grade. In addition thereto, since the chord performance of a embedded sound source chip has been enhanced, more sophisticated expression has been required for notification of an incoming call as one of use applications of a conventional loudspeaker. In addition, in recent years, voices, songs, and the like have also been used as lingua for incoming calls, and hence the demand for enhancement of the tone quality has more and more increased.
Here, when the mobile telephone is normally designed, there are two kinds of ideas, i.e., an idea of determining a position of a loudspeaker so as to correspond to the ear of an operator, and an idea of determining a position of a microphone so as to correspond to the oral cavity of an operator. In the usual way, the former is generally used because while an output of the loudspeaker can be specifically determined based on the performance of the loudspeaker and the setting for the mobile telephone, a sound picked up with the microphone can be freely adjusted by a loud voice of an operator. Thus, it is rare that the microphone is located in a position appropriately facing the oral cavity of an operator, and hence it is more likely that the microphone is located considerably apart from the oral cavity of an operator.
This tendency becomes more remarkable due to miniaturization of the mobile telephones. In a so-called candy bar type (straight type) miniature mobile telephone which comes into wide use in every corner of Europe and Asia, there are many ones in each of which the total length of the mobile telephone is shorter than a distance between the ear and the oral cavity of an operator.
If enhancement of sound collecting performance of the microphone is intended to be simply attained, then it is conceivable to use a more expensive microphone having higher performance. However, many inventions have been made in addition thereto. For example, it is described in JP 07-131849 A that sound holes are formed in a rear surface of a chassis of a mobile telephone to enhance the sound collecting performance.
In addition, in a flip type mobile telephone described in JP 08-097895 A, it is disclosed that a microphone is provided in a position where the microphone is exposed even in a state of closing a flip in a flip mounting section of the mobile telephone. A cavity within the flip of the mobile phone is defined, because of preventing the sound collecting performance from lowering even when the flip is opened.
In addition thereto, there is known a mobile telephone 1, as shown in FIG. 5, in which a slit 11 extends from sound holes 12 to the outside of a chassis.
However, when the sound holes are formed in the rear surface of the chassis as described in JP 07-131849 A, the light inundation is hard to avoid during rainfall or sweating. By one accident, the mobile telephone may not suddenly become unusable. However, it is also supposed that the operation of a part of functions of the mobile telephone, for example Photo function, become unusable by the long-term use in an abnormality.
In addition, as in the invention described in JP 08-097895 A, employment of a cavity structure for a movable section does not cause any of problems especially in the flip type mobile telephone that has no internal function in the ‘flip’.
However, this becomes a factor of reducing a design freedom for arrangement of components or parts in the folding type mobile telephone that include the various devices in both chassis.
Also, when the slit 11 from the sound holes 12 is led out toward the outside of the chassis as shown in FIG. 5, there is also a possibility of inundation through the slit 11.